Electric immersion heater



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M. C. FURSTENAU QLECTRI C IMMERS ION HEATER Filed Dec. 10, 1921 3 Sheets-Sheet 2 2 x v j x J a wg gg,

May 15, 1923. 1,455,246

M. c. FURSTENAU ELECTRIC IMMERSION HEATER Filed ec. 10. 1921 s sheets-shat '5 Patented May; 15, 1923.

UNITED STATES MARTIN C. FUBSTENAU, 0F PHILADELPHIA. PENNSYLVANIA.

ELECTRIC IMMERSION HEATER.

Application filed December 10, 1921. Serial No. 521,312.

T 0 all whom it may concern:

Be it known that I. MARTIN C. Fons- TENAU, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Electric Immersion Heaters, of which the following is a specification.

Various devices have been made prior to my present invention embracing the fundamental principle of heating by electrical resistance and these prior a'rt devices differed only in the method of construction and in assembling the various component parts requisite for the completed unit.

The object of so constructing these prior art devices was to allow them to be immersed in liquids for the purpose of heating the li uids.

rior to my present inventlon, however, it

was found to be practically impossible to construct such a heating device which would prevent the liquid or moisture from gradually working its way into the inner parts unless the outer parts wen: permanently sealed in such manner as to prevent the ready disassembling of the parts even though such disassembling would be necessary to inspect, repair, or replace any of the internal parts.

One object of my present invention is to provide an electric immersion heater which will be so constructed that the various component parts can be fabricated as individual elements without reference to the combination into which they may subsequently be combined to form a complete unit.

Another object is to so construct and arrange the various component parts that when they are assembled and put together they will form a perfectly watertight heating device which can be entirely submerged in a liquid without in any way damaging the parts of the heater or causing a short circuit in the electrical current due to moisture or a portion of the liquid having worked its way into the device.

A further object of my invention is to provide a heater which will be so constructed that the active heating portion thereof shall be insulated from the upper non-active or leading-in portion of the heater so as to eliminate the danger of burnt terminal wires or the danger of burning human hands if brought into contact with the terminals or casing should they become overheated.

A further object of my invention is to restrict as far as possible all of the heat generated by the resistance coil to the lower or active portion of the heater by insulating it from the upper or non-active portion; thus reducing the heat loss by radiation and increasing the heating efficiency of the apparatus by concentrating, in the lower or active portion of the heater, the heat generated by the resistance coil.

A still further object of. my invention is to so construct my improved heater that the operation of assembling the same can be carried out quickly and easily and that whenever necessary the various parts can be examined and if desired the combined parts can be readily withdrawn from the outer casing for examination, repairs or replacement without destroying or disarranging any part of the heater. ,7

These objects, and other advantageous ends which will be described hereinafter, I attain in the following manner, reference being had to the accompanying drawings in which- Figure 1 is an elevational view showing an immersion heater made in accordance with my resent invention,

Figure 2 is a sectional view taken on the line 2-2 of Figure 1,

Figure 3 is an enlarged sectional view showing certain of the parts illustrated in taken on the line 44 of Figure 3,

Figure 5 is a plan view of one of the separating disks which forms a part of my invention,

Figure 6 is a section taken on the line 6-6 of Figure 5,

Figure 7 is a view of the same general character as that shown in Figure 2 illustrating the heater cap as having been removed. said view also illustrating how the inner parts can either be removed from or replaced within the shell or casing,

Figure 8 is an elevational view partly in section showing the heating elements having been entirely removed from the shell or casmg,

Figure 9 is an elevation of one of the insuiating spacing tubes which forms a part of my invention, and

Figure 10 is a longitudinal section of one of said tubes.

Referring to the drawings, 12 represents a casing, which is preferably made of a length of seamless copper cylindrical tube 13, which has a bottom piece 14 brazed thereto at its lower end; said piece being in the form of a disk inserted and brazed so that its bottom surface is ilush with the lower end of the tube 13. The tube 13 at a position below its upper end 15 has a metallic heater nut 16 surrounding and soldered or brazed thereto and this .nut can be slipped downward into the proper position and secured in place as above described; the nut referably having an external screw threadbd portion 17 so that if desired the device can be screwed into any screw threaded opening if it is desired to permanently secure the device for the pur pose of radiatin heat at a position between the nut and the%ower end of the casing.

A disk of asbestos 18 isinserted within the casing so as to cover the inner surface of the bottom 14 of the casing and said disk is preferably made of such diameter as to fit within the tube 13, as clearly illustrated in Figures 2 and 7. A heating coil core 19, which may be made of porcelain, soapstone, or any vitreous material, is made in tubulai' form so as to provide a central longitudinally extending passage or chamber 20; said chamber extending entirely throu h the core from end to end. The outer sur ace of the core 19 is provided with a helical groove 21 preferably of V-shaped cross section.

Ducts or passages 22 and 23 lead inward from the opposite ends of the groove 21 into the chamber 20. An electric resistance heating wire 24 is wound within the turns of the groove so as to provide a heatin coil; said wire having a portion 25 w ich leads through the duct 23 into the chamber 20 and upward through said chamber; the portion 0 the wire at the opposite end of the coil having'a part 26 which leads through the duct 22 into the chamber 20 and then upward through said chamber. These ducts'are preferably formed at an abrupt angle to the longitudinal axis of the core 17 so that the portions 25 and 26 can be bent at an abrupt angle at the junction of the duets with the chamber 20; thus keeping the convolutions or turns of the coil snugly -within their -respective portions of the in asbestos separatin groove 21 at all times.

I preferably wind or wrap the outer part of t e core 19 with sheet mica 27 so as to insulate the entire outer surface of the core and coil wire'24. The end portions of the coil wire 24 are threaded through holes 28 disks; said disks being of such external iameter as to fit within the casing tube 13 and being arranged in laminated form one above the other; the

lower one of the disks abutting and covering the top end of the core 17. I have illustrated four of these disks as shown at 29. 30, 31 and 32; the extreme end portions of Two porcelain insulatin and spacing tubes 36 and 37 are then sipped over the a terminal wires 33 and 34 to allow the lower ends of said tubes 36 and 37to engage the upper surface of the disk 32; said up er surface of the disk 32 having annu ar grooves 38 surrounding the holes 28; said annular rooves bein such as to form a seat for 518 lower en s of the tubes 36 .and 37. It will also be noted that the soldered connection 35 between the coil wire ends and the terminal wires 33 and 34 are of such diameters as to fit therein and thereby keep the terminal wires'axially positioned within .the tubes and spaced from the inner wall of the tubes at positions above the 'solderin connections 35. The tubes 36 and 37 are 0 less length than the terminal wires 33 and 34 so that s. portion of the terminal wires projects above the upper ends of the tubes.

After the tubes 36 and 37 have been properly positioned an asbestos sealing washer or disk 39 is slipped down over the terminal wires; said sealing disk having holes 40 spaced apart through -which the terminal wires extend; said holes 40 being similarly arranged to the holes 28 of the other disks with the exception that said holes are slightly larger on account of the larger diameter of the terminal wires 33 and 34. The lower surface of the sealing disk 39 is provided with grooves 38' which are similar to the grooves 38 of the disk 32 so as to provide a centering seat for the upper ends of the porcelain tubes 36 and 37.

A heater terminal cap 41, which may be made of insulating rubber composition, hastwo internally screw threaded holes 42 and 43 which are-spaced apart to allow the terminal cap to he slid down over the terminal wires 33 and 34 so that said terminal wires respectively extend through the holes 42 and 43. The outer surfaces'of the terminal wires at positions above the top surface of the terminal cap 41 are coated with solder 41.

Coil wire terminal posts 44 and 45 each have the lower portions of their lengths externally screw threaded so that they can-be screwed respectivelyinto theholes 42 and 43 in the terminal cap 41 allowing the terminal wires, above the disk 39, to pass therethrough after which pressure can be applied tosqueeze or press-the parts so that the disks 29, so, 31 and 32 will bea ag gether with the tubes firmly pressing against the disk 32 and against thesealing-dlsk 39 with the terminal. cap pressing a ainstthe,

pp ee e sa inesl s A r i the heater terminal cap the upper end portion said parts are thus pressed together the upper ends of the coil wire terminal posts can be heated so as to melt the solder coating of the upper ends of the terminal wires and thus the terminal wires will be soldered to the terminal posts and said solder will form a complete seal between the outer surfaces of the terminal wires and the inner surface of the terminal posts.

The screw threaded portions of the terminal posts snugly fit within the screw threaded holes 42 and 43 and this screw' threaded connection is preferably made continuously long so that there is no possibility of moisture working its way inward to the disk 39. Furthermore, as will hereinafter be described, the disk 39 forms a fit with the inner wall of the tube 13 and then guards against the admission of moisture into the parts when arranged within the casing. The terminal cap 41 has an annular projecting flange 46 and at a position below this flange 46 the external diameter of the terminal cap is such as to snugly fit within of the casing tube 13 allowing the flange 46, which provides a shoulder, to engage over the upper end 15 f the casing tube, as clearly shown in Figures 2 and 3.

Vhen't-he parts are thus joined together as illustrated in Figure 8 they are inserted within the casing 12 so that the lower end of the heating coil core abuts the lower end of the casing; the peripheral edge surfaces of all of said disks fitting against the inner surface or wall of the tube 13 as does also the portion 42 of the terminal cap 41. The outer surface of the tube 13 below the top 15 is screw threaded as shown at 47 and a sealing clamp cap 48 has an internally screw threaded portion 49 which is adapted to be screwed on the screw threaded portion 47 of the tube 13. The sealing clamp cap 48 has an inwardly extending flange 50 adapted to abut the tofi surface 51 of the flange 46 of 41 so as to move and hold the lower sur ace 52 of the heater terminal cap flange 46 against the end 15 of the tube 13. When the parts of the heater proper, such for example as shown in Figure 8, are secured together, it is preferable that the distance between the lower end of the core 19 and the surface 52 of the flange 46 of the terminal cap 41 is slightly greater than the distance between the top of the disk 18 in the casing and the upper edge 15 so that when the sealing clamp cap is screwed upon the upper end of the tube 13, the flange 50 thereof will engage the surface 51 of the flange 46 of the heater terminal cap 41 and force the shouldered surface 52 of said flange 46 into firm sealing engagement with the end 15 of the tube 13. During this action the various interposed parts of the heater, such for example as the disks,

the tubes, the coil core, and the heater terminal cap 41, will be placed under compression and such action will cause the disks to slightly expand into firm contact with the inner surface of the casing.

It will be noted that when the parts are thus assembled there will be a space 53 between the upper separating disk 32 and the sealing disk 39 and this space also will surround the tubes 36 and 37. This space 53 constitutes a dead air space forming a superior kind of insulation bet-ween the direct heating part, including the heating coil, and the upper part of the device. Further than this, the disks 29, 30, 31 and 32 pro- 9 vide an excellent heat insulating medium so that while the lower part of the device when in use becomes extremely hot, the upper part is comparatively cool and can be readily handled without danger of burning or in-,

convenience to the user. The coil core with the insulating wrappings of mica thereon is preferably made of such diameter that when cool, it will readily slip within the casing; the core. when heated. expanding and serving to fit firmly in the casing within its length when the device is in use.

The terminal cap flange 46 provides a shoulder that rests on the outer casing as above described and forms with it a watertight joint since it is firmly held in place by the sealing clamp cap 48 The leadingin or terminal wires are also made watertight by being soldered to the ends of the terminal posts; thus effectually sealing the heater against the possible ingress of moisture and making of the whole a perfectly watertight construction.

By interposing the series of insulating separator disks through which the heating wire passes to and from the coil of the core. an. effective heat insulating means is provided. B v arranging and tonstructing the core with the central chamber 20 not only is provision made for the upward extension of the wire but a dead air space is produced: thus eliminating the major portion of the heat which is usualy carried to the upper non-active or leading-in end of the heater. As a further precaution the leading-in wires are incased in the separated tubes of insulating material and the ends of these tubes are closed by the disks. Thus these tubes are closed top and bottom: -the leading-in wire passing through the dead air space pro- .vided in the tubes.

' If, after use of the device. it is desired to inspect any of the parts. it is merely necessary to unscrew and remove the sealing clamp cap 48, after which the entire heating structure proper can be removed from the casing in a manner shown in Figure 7 and the parts will all be held together inthe position as shown in Figure 8 so that they can again be replaced in a very short ,ready fonuse.

.closed at the other end;

Any suitable form of connecting device canbe attached to the projecting portions of theterminal posts for supplying current to effect the heating of the coil. In addition to this, when the parts are assembled, a

strong device is provided which can be roughly handled without injuryto any of the parts since they are protected by the casing and the sealing clamp cap.

By having the ends of the tubes either of semi-circular, conical or tapered cross section they serve as centering portions for coaction with the contacting disks not only facilitating assembly of the parts but also serving to keep the tubes in proper spaced relation with each other and with the terminal wires which extend therethrough.

While I have described my invention as taking a particular form, it will be understood that the various parts of my invention may be changed without departing from the spirit thereof, and hence I do not limit myself to the recise construction set forth, but consider t at I am at liberty to make such changes and alterations as fairly come within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is 1. In an electrical resistance heater, a casing closed at one end, an insulating core disposed at the closed end of the casing and having an internal space; electrical resistance heating means within the casing and outside the core, and heat-resisting means insulating the heating unit from the remainder of the casing and closing the space in the core thereby establishing a dead air space in the heating unit; substantially as described.

2. In an electrical resistance heater, a casing closed at one end and adapted to be a heating unit in the closed end of the casing; heat resisting means insulating the heating unit, and heat resisting means spaced therefrom closing the casing and establishing a dead air space between the heating unit and the terminal cap; substantially as described. 3. In an electrical resistance heater, a casing; an insulating core within the casing and having an internal space; electrical resistance means outside the core; insulating means separating the heating unit from the remainder of the casing and closing the space in the core thereby establishing a dead air space within the heating chamber, and other insulting means spaced from the first named insulating means and closing the casmg thereby establishing a second dead air space within the casing; substantially as described.

adapted to be closed; a heating unit immediately enclosed by the closed end" of the casing; a detachable cap. for closing the easing, and connections between the cap and the heating unit wherebythe latter may be withdrawn from its casing; described.

5. In an electrical resistance heater, a

casing having a closed end and an" end adapted to be closed; a heating unit immediately enclosed by the closed end of the casing; heat resisting means insulating the heating unit from the remainder of the casing; a detachable'cap adapted to close the casing, and connections between the cap, the heat resisting means and the heating unit whereby the heat resisting means and the heating unit may be withdrawn from their casing; substantially as described.

6. In an electrical resistance heating device, a casing; a heating agent within said casing; a separating insulating structure fitting within said casing and interposed besubstantially as tween said heating agent and another portion of said casing; an electrical conductor leading through said latter portion of the casing and through said separatin structure to supply electricity to said eating agent; a second separating insulating structure spaced within said latter portion of the casing from said first separatin structure to provide a deadv airspace t rough which sald conductor passes; and a tubular structure surrounding said conductor between said separating structures; substantially as described.

7. In an electrical resistance heating device, a casing; a heating a cut within said casing; 11, separating insu ating structure fitting within said casing and into ween said heating agent and another portion of said casin an electrical conductor leading throng said latter portion of the casing and through said separating structure to supply electricity to said heating agent; a second separating insulating structure spaced within said latter portion of the casing from said first separating structure to provide a dead alr space through which said conductor passes; and a tubular structure surrounding said conductor between said separating structures, said tubular structure having its ends in engagement with said separating structures; substantially as described.

8. In an electrical resistance heating device, a casing; a heating agent within said casing; a separating insulating structure fitting within said casing and interposed between said heating agent and another portion of said casin an electrical conductor leading throng said latter portion of the'casing and through said separating structure to supply electricity to said heating agent; a second separating insulating structure spaced within said latter portion of the casing from said first separating structure .to provide a dead air space through which said conductor passes; and

a tubular structure surrounding said conductor between said separating structures, said tubular structure having its ends in engagement with said separating structures and having its outer surface spaced from the inner wall of said latter portion of the casing; substantially as described.

9. In an electrical resistance heating device, a. casing; a heating agent within said casing; insulating means within said casing between said heating agent and a portion of said casing providing an opening; a cap extending into said casing through the opening, said cap having a shouldered flange for engaging a part of the casing surrounding said openin and means detachably connected to said casing and-having a part adapted to hold said shoulder in sealing engagement with said portion of the casing surrounding the opening; substantially as described.

10. In an electrical resistance heating device, a casing; a heating agent within said casing; insulating means within said casing between said heating agent and a portion of said casing providing an opening; a cap extending into said casing through the openin said cap having a shouldered flange or engaging a part of the casin surrounding said opening; means detac ably connected to said casing and having a part adapted to hold said shoulder in sealing engagement with said portion of the casing surrounding the opening; and an electric conduit extending through said cap and insulating means to said heating agent for supplying electricity thereto; substantially as described. a

11. In an electrical resistance heating de: vice, a casing having an open end; a heating agent within said casing; means for insulating said heating agent from a portion of the casing including said open end. said insulating means including apart for closing said open end; and means detachably connected to said casing for engagement with said part for holding it in sealing engagement with said open end of the casing; substantially as described.

12. In an electrical resistance heating device, a casing having an open end; a heating agent within said casing; means for insulating said heating agent from a portion of the casing includin s'aid open end, said insulating means inclu ing a part extending into said casing and another part for closing said open end; and clamping means detachably secured to said casing and adapted to compress said insulating means into sealing engagement with said casing; substantially as described.

13. In an electrical resistance heating device, a heating agent; an insulating disk structure covering said heating agent; conduit wire insulating tubes positioned over said disk structure; and a second disk structure positioned above said tube; substantially as descibed.

14. In an electrical resistance heating device, a heating agent; an insulating disk structure covering said heating agent; conduit wire insulating tubes positioned over said disk structure; and a second disk structure positioned above said tubes, said tubes having their ends tapering in cross section whereby they will center themselves in said disk structures; substantially as described.

15. In an electrical resistance heating device, a casing; an electrical resistance heating agent therein; an insulating disk structure covering said agent; insulating means spaced above said disk structure and including a cap of insulating material; hollow terminals firmly screwed in said cap and forming ducts; and electric conduit wires extending through said lateral terminals and insulating disk structure to the heating agent. said conduit wires being soldered in said terminals to provide a watertight electrical contact with the same; substantially as described.

16. In an electrical resistance heating device, a casing; an electrical resistance heating agent therein; an insulating disk structure covering said agent; insulating means spaced above said disk structure and including a cap of insulating material; hollow terminals firmly screwed in said cap and forming ducts; electric conduit wires extending through said lateral terminals and insulating disk structure to the heating agent, said conduit wires beingsoldered in said terminals to provide a watertight electrical contact with the same; spacing tubes interposed between said disk structure and the upper insulating means and through which said conduit wires extend; and a sealing clamp cap in screw threaded connection with said casing and having a portion adapted to engage said insulating cap; substantially as described.

17. In an electrical resistance heating device, a casing; an electrical resistance heating agent therein; an insulating disk structure covering said agent; insulating means spaced above said disk structure and including a cap of insulating material; hollow terminals firmly screw in said cap and forming ducts; electric conduit wires extending posed between said disk structure and the upper insulating means and through which said conduit wires extend, said insulating cap having a shouldered flange for abutment with the open end of said casing; and a sealing clamp cap in screw threaded connection with said casing and operative to move said flange of the insulating cap into sealing engagement with said casing at a position surrounding the opening therein; substantially as described.

18. In a heating device of the character described, a tubular casing having an open end; a heating agent in said casing opposite said open end; an insulating separating structure fitting within said casing between the heating agent and said open end of the casing and having a portion closing said open end; and means in clamping-enga ement with said casing and having a art or forcing said closin portion into sea in .en-

- gagement with sai casing; substantial y as described, a tubular casing end; a heating agent in said casing opposite described.

19'. In a heating device of the character described, a tubular casing having an open end; a heating agent in said casing opposite Said open end; an insulating separating structure fitting within said casing between the heatin agent and said open end of the casing an having a portion closing said open end; and means in screw threaded engagement with said casing and having a part for forcing said closing ortioninto sealing engagement with sai open end of the casing; substantially as described.

20. In a heating device of the character having an open said open end; an insulating cap having a portion extending through said open end into the casing and a flange abutting said open end; and a clamping cap in screw threaded engagement with said casing and operative to hold said flange in sealing engagement with said open end of the casing; substantially as described.

21. In a heating device of the character described, a tubular casin having an open end; a heating agent in said casing opposite said open endan insulating cap having a portion extending through said open end into the casing and a flange abutting said open end; a clamping cap in a screw threaded engagement with said casin and operative to hold said flan e in sea ing engagement with said open en of the casing; hollow terminal posts screwed into said insulating cap; and electric conduit wires soldered in said posts and leading into said casing for supplying electricity to said heating agent; substantially as described.

22. In a heating device of thecharacter described, a tubular casing having an open end; a heatin agent in said casing opposite portion extending through said open end into the casing and a flange abutting said open end; a clamping cap in screw t readed engagement with said casing and operative to hold said flange in sealing engagement with said open end of the casing; hollow terminal posts screwed into said insulating cap; electric conduit wires soldered in said posts and leading into said casing for supplying electricity to said heating agent; an insulating disk structures fitting transversely within said open en an insulating cap having a portion extending through said open end into the casing and a flange abutting said open end; a clamping cap in screw threaded engagement with said casing and operative to hold said flange in sealing engagement with said open end of the casing; hollow terminal posts screwed into said insulatin cap; electric conduit wires soldered in said posts and leading .into said casing for supplying electricity to said heating agent; and insulating disk structures fitting transversely within said casin between said heating agent and the insulating cap, said disk structures being spaced apart within the length of the casing; substantially as described.

24. In a heating device of the character described, a tubular casing havingan open end; a heating agent in said cas ng opposite said open end; an insulating cap hav a portion extendin through said 0 diid into the casing an a flange abutting said open end; a clamping cap in'screw threaded ollow plying electricity to said heating agent; in S11 I ating disk structures fitting transversely within said casing between said heatin agent and the insulating cap, said conduit wires extending through said disk structures; and insulating tubes through which said wires pass between said disk structures, said tubes leading from one disk structum to other; substantially as described.

25. In a heating device of the character described, a tubular casing having an open end;'a heatin agent in said casing op '08 said open en an insulating ca having a portion extending through sai open end into the casing and a flange abutting said open end; a clamping cap in screw threaded engagement with said casing and operative to hold said flange in sealing enga ment with said open end of the casing; w

Ill

10 wires pass between said disk structures, said wires being connected to said heating agent;-

substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

MARTIN c. FURSTENAUQ Witnesses:

CHAS. E. Po'r'rs, ELIZABETH GARBE. 

